I don't miss EU3-style sliders. They show how incremental change is, but arguably are too static. EU3 (and EU2) also had leaders, as well as sliders.
I think leaders really hit their stride in EU4 with the DLC that added ruler personalities, which affect AI decisions as well. Does the ally of an enemy have a Cruel ruler? Maybe you can get them to dishonor their alliance. Did France just get an Aggressive Naive Enthusiast? Hello Napoleon wannabe! Etc. It takes it from "a set of stats a country is stuck with for a while, for better or worse" to "has a meaningful impact on gameplay as well".
I'd be interested in alternative games focused on the same time period. I think the ones there are tend to be focused on more particular aspects of it - e.g. Port Royale focuses in the Caribbean geographically, and trade/pirates thematically. More competition and options is a good thing. That did eventually come to Civilization, with Humankind in particular, but only after an extended period where a significant minority of the fan base was less than pleased with Civ V and Civ VI; there were also more studious producing thematically different games in the same particular genre (4X) in Civilization's case than I'm aware of in the pauseable-grand-strategy-RTS space.
I hadn't heard of Grey Eminence. Looked it up. I agree with those who've said it looks incredibly ambitious for a project from a group of modders, although at least it's the MEIOU modders. The guy listed as lead developers has it listed on his LinkedIn from January 2020 - January 2023, so it has had some time in the oven, but also based on his LinkedIn he isn't on it anymore (couldn't find the LinkedIns for the other developers listed on the project's site). Conceptually, it certainly looks interesting, but with these sorts of projects it's always, "is there the wherewithal to see it through to where it's complete enough and an enjoyable game to play?" The fact that its Patreon is raking in $2K/month and that it was being worked on for 2+ years prior to the Patreon launch suggests it has been funded largely through the founder's YouTube profits. Which, hey, those can be substantial, but it's probably not as good as Humankind being developed by the Endless Legend/Space developer with earnings (including ongoing ones) from those games, with some additional funding from Sega.
In other words their first need is having the funding to have people on it full time (I've been on a project to create an open-source alternative to a Civ game; the greatest hazard to games developed by modders are their day jobs), and then having the expertise. It can work, Kingdom Come: Deliverance being a good example (and one with many industry veterans involved in the project, followed by substantial funding from a rich Czech guy to get it to the finish line), but I'd like to see more hard evidence, including that losing the guy listed as the lead developer isn't too big of a problem.